[PoorMansXcuse]

Ok so back story is I bought my car about 3 years ago with a 305 with a performer intake and rv cam. It's reasonably quick with 3.73s but I wanted a little more so I bought a 350 to swap in. I don't have the time or space to build it though so it's been sitting in a shed. I honestly don't need 400hp to cruise around on a nice Saturday and have been thinking about sticking with what I have. I've been getting the tinkering bug lately though.
I have some vortec heads I bought for the 350 and am thinking about putting them on the 305 since that's something I can do with what I already have. I'll be taking care of the exhaust at the same time.
The cr with 58cc heads is 9.5:1 & the new ones are listed at 64cc but I've read they're usually closer to 62. I don't want to mill the heads in case I do end up using them on the 350. How much cr will I lose with a .015 gasket? I've heard different specs for the factory gasket but the most common is .028.
I have a q jet on the car right now and a 600 edelbrock 1405 laying around. I don't have any problems with the current carb but it really limits what intake I can use. I'd like something more performance oriented than a performer style. Maybe the summit stage 2. How will the 2 carbs compare in this application?
Any guesses how much power to expect out of this combo?


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[Steve R]

Have you factored in the cost of a manifold that will fit Vortec heads. When you add up the costs involved with the swap the money might be better spent on your 350 or buying an inexpensive crate motor. If those aren't an option think about limiting your modifications to those that will directly bolt onto the 350 or spending a bit of money to make sure your 305 is dialed in.

Steve R

 

[PoorMansXcuse]

I only have a gravel driveway to work with right now so pulling the motor isn't going to happen for a while. I would have to buy an intake anyways to put together the 350 so I'm not counting that as an expense. I'd rather not spend $400 on the q jet rpm though. I am trying to make sure that everything I use will transfer over to it. I don't like wasting money either. I'm thinking the only extra things I'll end up buying is gaskets.


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[T_R]

You can pull a motor in a gravel driveway. Just use a 4x8 sheet 3/4" plywood to roll your hoist on. I did it twice before I built my garage. It wasn't a big deal. It makes more sense to do that than swap heads then take them off again and swap engines.

 

[64SS427]

GM called their engines Vortec for a long time, 20 years or more I think. What are your head casting numbers? 305's have small bores. Will the valves the 350 heads clear them? You will lose compression, which is torque. Is it worth it to gain a little flow?

Devin

 

[blue_69_malibu]

First, I would NOT buy that Summit carb. Get a proper Holley, Edelbrock, or whatever floats your boat.

Second, the thickness of your head gasket and your compression ratio change is almost meaningless for this project, IMHO. You'd more than make that up with better, Vortec heads. FWIW, keep in mind that going Vortec is great.....but you'll spend more $$$ than you think at first. Intake manifold, rocker arms, valve covers all have to change. Some mounting brackets that need the "old" intake bolt pattern to mount will not work without modification.

Having said that, when I had the factory 307 in my Malibu, I did NOTHING to it. Instead, I saved up for a 350 and slowly acquired the pieces that I needed for my swap. From my point of view (which will be different from many) any time or money that I spent on my 307 was a waste. Instead, I focused my time and money on the 350 and simply tolerated the 307 in the meantime. When I finally got around to my 350, it was....awesome. I have no regrets at all about how I did things.

Lastly, no one NEEDS a 400HP motor to go cruising on a Saturday....but it sure is fun!!

 

[Busted Knuckles]

Leave the 305 as it is. No need to throw good money after bad.
Take your time and build a stroker out of your 350 block and use the Vortec heads. None of us NEED more than 400hp on the street, but we all WANT more than what we have and once you get used to a warmed over 305, you'll WANT more.

 

[ddeennis]

Ok so back story is I bought my car about 3 years ago with a 305 with a performer intake and rv cam. It's reasonably quick with 3.73s but I wanted a little more so I bought a 350 to swap in. I don't have the time or space to build it though so it's been sitting in a shed. I honestly don't need 400hp to cruise around on a nice Saturday and have been thinking about sticking with what I have. I've been getting the tinkering bug lately though.
I have some vortec heads I bought for the 350 and am thinking about putting them on the 305 since that's something I can do with what I already have. I'll be taking care of the exhaust at the same time.
The cr with 58cc heads is 9.5:1 & the new ones are listed at 64cc but I've read they're usually closer to 62. I don't want to mill the heads in case I do end up using them on the 350. How much cr will I lose with a .015 gasket? I've heard different specs for the factory gasket but the most common is .028.
I have a q jet on the car right now and a 600 edelbrock 1405 laying around. I don't have any problems with the current carb but it really limits what intake I can use. I'd like something more performance oriented than a performer style. Maybe the summit stage 2. How will the 2 carbs compare in this application?
Any guesses how much power to expect out of this combo?


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So I ran the numbers and swapping over to 350 vortec heads of the 906/062 design is pretty much a wash on compression when using a steel shim gasket .015" and assuming 62 cc's, now if they are 64 cc then looking at .1-.2 drop in compression. Your still power ahead because of the better heads.

I did this swap on a 350 for dirt cheap, I bought two sets of vortec heads for 80 bucks, I researched both casting that what I had and found out they are the same, so I picked the cleanest set of the two.

I took the vortec heads apart and filed down the valve guides with a flat bastard for more lift clearance, I got a spring kit.

Vortec Head Spring/Retainer Kit - Straub Technologies

I hand lapped the valves in to clean up the pitted seats til they looked good. I was done with heads.

i f I was to do it again I would just file down the guides and just buy new springs for about 35 bucks and be really cheaper than the kit, being first time down the vortec road I did not know how the kit was getting it's clearance, so you could save a few bucks just doing some manual labor.

So no real money in the heads, in fact I sold the other pair on craigslist for 100 bucks.

With a little longer search you can probably find cheaper, but I saw these, less than 30 bucks for your steel shim gasket.

Felpro 7733SH1 Steel Shim Head Gasket Small Block Chevy 4 100 034 Bore 016 034 Thick | eBay

depending if you have rocker arms, if you need to buy some I got something like these for dirt cheap. 60 bucks

Chevy SBC 350 1.5 Ratio 7/16" Self Aligning Steel Roller Tip Rocker Arm Set

So now you should be able to slap the heads on and lash the valves, so this leaves for the intake which I bought a cheap 100 dollar rpm knock off at the time I found on ebay it was a display model, I did a quick search on ebay theres a 160 dollar cross wind intake that's just like I bought.

Professional Products 52028 Crosswind SB Chevy Vortec Aluminum Intake Manifold | eBay

So then I would invest in a very good carb you can later carry over to your 350, so I would get a very nice 750 holley vacuum secondary, even for your 305, your not going to kill a thing, about everyone on the planet would say go with a 600 cfm carb and 750 will kill the engine, HOGWASH, I have done several track outing thru my life and my sons 305 ran great with a 750 holley ( we went from a nice 600 holley I built for him to my old friend 750 cfm I have had for decades and his car didn't slow down one bit).

Valve covers, go find some stockers and clean them up, I got some for free from a friend who was going to toss them, so you might be able to do the same.

What the cost, not much around 350 bucks and a learning life lesson, you might be able to sell your current carbs and invest in a nicer 750 holley, you should be able to pick one up from ebay or craigslist for under 200 used- cheaper if you can rebuild them, I see fine good examples often or you can dish out about 300-350 for a new one.

Hope this helps and every part transfers over to a 350, so your just pre fitting your top end on a 305 is all.....lol


Hope this helps

 

[PoorMansXcuse]

Good info thanks. I got the heads complete off a guy that bought the 330 hp gm crate motor, wasn't happy after the first drive and upgraded to edelbrocks. Really wish I'd asked him about the intake cause he probably would have thrown it in free. Cost me $350 with chrome gmpp valve covers & Selling my old heads almost covered that. I was thinking the same thing about the 750 holley. I wouldn't really need to do that right away either so I can wait for the right deal to come along. If nothing else I'd end up with a nice looking engine bay.


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[PoorMansXcuse]

I found a performer rpm for a great price. That pretty much rules out the q jet but I really didn't want a low rise manifold that would be a limitation down the road.


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[cv67]

So use a 10 adapter plate
Vottecs dont come with big valves ignore the 58 vs ?? CC have em shaved.
Thre craz sever porting on 305 heads DONT WASTE YOUR TIME they are crap plain and simple
Get a set....make em work get anice power increase. OR if you can make things very easy and get a 350.

You can do oral surgery through one of two holes which is the easiest old saying


You can tell guys win or lose well its a305. Noone cares you win you win thats what its all about. Why spend money if youre not happy with the results
Some may disagree but after 50 yrs Ive done EVERYthing wrong many time with builds. Do it right...make it easy .Go big as you possibly can thats WHERE its at period. Have fun:thumbsup:

 

[hereinmissoula]

Can still use qjet with adapter/spacer... But don't .... Just bite the bullet and get 750 Holley double pumper... I personally am not a fan of vac secondaries , have always picked up going to mech.

I have found used ones on eBay or Craigslist for under 100.00 that need rebuilt. Just run the numbers on the front to identify.

Buy a quick fuel/aed/Holley rebuild kit. Take apart and soak everything in half pinesol half water for 2-3 days , pressure washer/rinse off. Perfect . Easy .

Or buy one new. In my opinion edelbrocks suck for performance, Holley always makes more power .

Vortecs are great heads and if your 305 has good compression and you pair it with a cam swap , xe268, voodoo equivalent.. Or isky .450 lift rule cams work well with vortecs... Just keep duration under low 230's. Cheap cam swap under 200.00 including lifters . I like the Delphi lifters skip white sells. Quality and cheap. Make a huge difference.

Headers are a must .

And shave the vortecs till the machinist hits valves .. More compression with the 350 won't matter , just add more cam (more overlap/duration)when you build it. 10.5 vortec 350 on pump doable with right cam ......

Rpm intake (or like) .... Got a good running engine.....

My .02

 

[hereinmissoula]

And more money ($100.00) but Alex parts sells drop-in spring kits good to .550 I believe . Worth it to me unless u got the time to mod heads yourself.

 

[jeff swisher]

If you are thinking the Performer RPM is a limitation down the road you are wrong thinking that.

The RPM is an excellent manifold with a Q jet or Edelbrock or Holley.
Just tune the carb.

Here is one for ya.
355" chevy 252@ .050" solid flat tappet 1.6 roller rockers .571" lift 106LSA ported 601 casting 305 heads 1.94-1.60 Valves.
cast rebuilder pistons.

.. Victor JR intake was tried ran it with 750 Q jet and 800 DP holley.. turdish everwhere.. 1" and 2" and 3" spacers tried.
Ported iron Q jet intake was then tried...Man that thing woke up.. many spacers and the 2 carbs were tried.. it did not care as long as you had 2" of spacers it ran the same with both carbs.

Holley strip dominator was then tried with both carbs and a 750 carter AFB.
Carbs were a wash but man great power.. a little bit better than the highly ported Qjet intake.

Then a Hurricane intake was stuck on to it with 4 corner cooling.. not quite the power as the Strip Dominator.. but more than the Qjet.
Guy stuck with the Holley 800 as the other carbs were mine and it did not matter which one was on it.

Ran mid 11's 3000 lb 411 gears 3500 stall .

All carbs can run very well in the right hands.. you just need to know the carb.. so get one you know how to tweak.
If you do not know how to tweak ,, get a how to book on the subject.

It will be the best 20 bucks you can spend.

 

[hereinmissoula]

If you are thinking the Performer RPM is a limitation down the road you are wrong thinking that.

The RPM is an excellent manifold with a Q jet or Edelbrock or Holley.
Just tune the carb.

Here is one for ya.
355" chevy 252@ .050" solid flat tappet 1.6 roller rockers .571" lift 106LSA ported 601 casting 305 heads 1.94-1.60 Valves.
cast rebuilder pistons.

.. Victor JR intake was tried ran it with 750 Q jet and 800 DP holley.. turdish everwhere.. 1" and 2" and 3" spacers tried.
Ported iron Q jet intake was then tried...Man that thing woke up.. many spacers and the 2 carbs were tried.. it did not care as long as you had 2" of spacers it ran the same with both carbs.

Holley strip dominator was then tried with both carbs and a 750 carter AFB.
Carbs were a wash but man great power.. a little bit better than the highly ported Qjet intake.

Then a Hurricane intake was stuck on to it with 4 corner cooling.. not quite the power as the Strip Dominator.. but more than the Qjet.
Guy stuck with the Holley 800 as the other carbs were mine and it did not matter which one was on it.

Ran mid 11's 3000 lb 411 gears 3500 stall .

All carbs can run very well in the right hands.. you just need to know the carb.. so get one you know how to tweak.
If you do not know how to tweak ,, get a how to book on the subject.

It will be the best 20 bucks you can spend.

Only place you will find anything other than a Holley design carb a true performance/race motor is a class rule engine.... Ex. Super stock with qjet....

Holley dp will always pick up in my experience...

JS

 

[hereinmissoula]

I made over 500hp 500 tq with 230 Hyd roller 406 afr195 QuickFuel 750 rpm intake.

Agree Rpm will support quite a bit of power .

 

[PoorMansXcuse]

The rpm won't limit me down the road & I didn't want something like a regular performer is what I meant to say. I also want to learn more about carb tuning. My plan is to keep an eye out for a holley 750 & mess around with the eddy in the meantime to see what I can get out of it.


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[jeff swisher]

I have over 50 carbs at my disposal and tuned they will all be within 10 HP of each other, as long as you are not under carbed.

This dyno comparison between Q jet and 3310 Holley. AFR withing .5 of each other.. very interesting.
400 Dyno Test Data with Holley & Q-Jet Comparison - Pontiac GTO Forum

Buddy swore by the Holley 750 Said my old Nova would be quicker with it than my Carter AFB.
I let him install the Holley and tune it.. he even had the Perceys blocks and the trick plastic air entry thing on it.

The 750 Holley laid down way early in the RPM range Like 700 rpm sooner than my AFB.

No tweaking fixed it.

I later scored a cheap 3310 and began to tune it myself and it never had the top end pull 7000+ RPM that my Q jet or The carter AFB would produce.

Not one to give up without a fight I began modifying the 3310.
First the air horn.. then thinned the throttle shafts and installed smaller screws in the throttle blades.

That made the carb charge much harder on the big end..Then I began polishing and reshapog the venturies a bit.
It got even better.
Now it was basically tied for power throughout the RPM range as my other carbs.

I normally shifted that little 350 at 7600 rpm and it would keep pulling without nosing over past 8000 rpm
Which I found out by letting a buddy drive it..

I later scored a 4779 double pumper with down leg boosters.
That carb was no better than the stock 3310 in the upper rpm area.
It got the same treatment and then some..I enlarged the venturies and it has some epoxy work to the front venturi entry.

In stock form the 750's never had the stuff i needed ... but I made them work..
You tweak enough carbs you will find what works and what does not.

I had all the HP books on carbs.. well between me and a buddy we had many books on chassis transmissions engines and carbs.

Have fun in your quest.
One more.
327-.060 small journal XE270Roller AFR eliminator 180 heads.. rpm intake 421 HP and tq was like 419.
3 carbs tried..
2 Holleys one was the carb the dyno shop owned.. old faithful it always made great power.

The third carb was a 750 edelbrock I built for the engine when it had 268XE and ported 492 heads.
The dyno shop built the engine and was breaking it in and dynoing it and did not want to try the 750 edelbrock,,, but my buddy insisted.
They were all amazed that it made more power everywhere than the other 2 carbs.. and they tuned one of the carbs to try to maximize the HP.

It is what it is.
I like carbs,, Just about all of them.

 

[hereinmissoula]

I have over 50 carbs at my disposal and tuned they will all be within 10 HP of each other, as long as you are not under carbed.

This dyno comparison between Q jet and 3310 Holley. AFR withing .5 of each other.. very interesting.
400 Dyno Test Data with Holley & Q-Jet Comparison - Pontiac GTO Forum

Buddy swore by the Holley 750 Said my old Nova would be quicker with it than my Carter AFB.
I let him install the Holley and tune it.. he even had the Perceys blocks and the trick plastic air entry thing on it.

The 750 Holley laid down way early in the RPM range Like 700 rpm sooner than my AFB.

No tweaking fixed it.

I later scored a cheap 3310 and began to tune it myself and it never had the top end pull 7000+ RPM that my Q jet or The carter AFB would produce.

Not one to give up without a fight I began modifying the 3310.
First the air horn.. then thinned the throttle shafts and installed smaller screws in the throttle blades.

That made the carb charge much harder on the big end..Then I began polishing and reshapog the venturies a bit.
It got even better.
Now it was basically tied for power throughout the RPM range as my other carbs.

I normally shifted that little 350 at 7600 rpm and it would keep pulling without nosing over past 8000 rpm
Which I found out by letting a buddy drive it..

I later scored a 4779 double pumper with down leg boosters.
That carb was no better than the stock 3310 in the upper rpm area.
It got the same treatment and then some..I enlarged the venturies and it has some epoxy work to the front venturi entry.

In stock form the 750's never had the stuff i needed ... but I made them work..
You tweak enough carbs you will find what works and what does not.

I had all the HP books on carbs.. well between me and a buddy we had many books on chassis transmissions engines and carbs.

Have fun in your quest.
One more.
327-.060 small journal XE270Roller AFR eliminator 180 heads.. rpm intake 421 HP and tq was like 419.
3 carbs tried..
2 Holleys one was the carb the dyno shop owned.. old faithful it always made great power.

The third carb was a 750 edelbrock I built for the engine when it had 268XE and ported 492 heads.
The dyno shop built the engine and was breaking it in and dynoing it and did not want to try the 750 edelbrock,,, but my buddy insisted.
They were all amazed that it made more power everywhere than the other 2 carbs.. and they tuned one of the carbs to try to maximize the HP.

It is what it is.
I like carbs,, Just about all of them.

Not doubting u , what your saying ... But why is a qjet or and afb on ANY race engine ... From drag to dirt...? Only when a class specifies it

And in my personal experience (I'm a good tuner , but a carb guru I am not, though I completely understand how they operate , holleys anyways) and it hasn't even been close .

Have picked up big at the track. Over a half second on a solid roller 355, iron eagle 215, 250 shot Auto 4.10 gears th400 4000 stallOwner had 750 edelbrock on it . No dyno.

Maybe I'm lost .....

 

[jeff swisher]

My buddy ran a 750 edelbrock on his 355 flat tappet.
The one I spoke of in earlier post.. he tuned and tuned to his best wit.
And came over to me in the pits while I was working on another friends car and said : That is it, that is all she has in her.
I made many passes tried different jetting and timing and she will not go any quicker.

I said bring the vehicle over to me.
I pulled out his primary jets which in my mind were way too large.. but his plugs were clean white.. probably due to the super hot ignition system he was running.

I jetted it down and told him go make another pass.
He did and came back with a huge grin on his face. It went .4 quicker.

Each engine likes what it likes that is fact.. and I do know if you need more than 800 cfm a Holley is a great place to find it.
But i usually grab 2 of the carter AFB carbs when I need more.

The Q jet downfall is small fuel bowl.. you can go through that fuel quickly with stock needle and seat.
The AFB/ Edelbrock performer does not really like to take hard corners.. fuel slosh is horrible .. so not optimum on the track compared to a Holley or Qjet.

For all around off road and drag strip it will be hard to beat a Holley.
For a fact it is a very versatile carb easy to convert to E85 and back.

When I was 17 I got a 396 425HP that was modified with different cam and tunnel-ram and ran 9.8 seconds in a chevelle
It had 2 750 carter afb carbs.
I was kind of hooked on them after that, so that is probably why I like them most.. If it was equipped with 660 center squirters I would probably like them.

One thing for sure I like carbs better than FI.
Of course in 10 years that may change.