Proposed Engine Spec: Another Gen 1 357

[skinny z]

I'm getting closer to another small block for the Camaro.
Here's a list of parts (both real and imagined...).
The objective is for peak HP at ~5900 RPM. If all goes according to plan, racing revs will be between 4500 (converter flash stall) and 6300 or so.
It's not strictly a drag racing engine but for all intents and purposes, let's say it is.

Top to bottom:
750 CFM Barry Grant VS carb.
RPM Air Gap (for Vortec heads).
RHS Pro Torker iron heads.

RHS AMS.jpg

.040" OEM block.
Wiseco PTS503A4 flat top piston, .014" down.
Elgin forged rods 5.7".
Factory forged crank (10/10). Nice fillet.
Compression ratio target is 10.25:1.
Cam spec: 280/280, 108 LSA on a 104 ICL. (Haven't dialed in the .050"-.200" numbers as of yet). Lift at ~.550".
Crower SS 1.6 ratio rockers.
COMP 26918 spring and tool steel retainers (or possibly PAC equivalent).
1 5/8" mid-length header with collector extensions (open exhaust).

Seems fairly average.
As stated the objective is for peak HP at ~5900 RPM.
I'd say HP and TQ will both fall in around 450 as seen on an engine dyno. Also hoping it's essentially flat for the rev range specified.
Does this look to be a doable undertaking? Specifically speaking, are the heads up to it?
This has been built virtually and for the most part also tested in the chassis with the exception of the cam and open headers.
I'm looking for opinions on the engine combo and not necessarily the car itself. Let's call it a DIY crate engine.
Sorting out the chassis will come later.

[1980RS]

I'm getting closer to another small block for the Camaro.
Here's a list of parts (both real and imagined...).
The objective is for peak HP at ~5900 RPM. If all goes according to plan, racing revs will be between 4500 (converter flash stall) and 6300 or so.
It's not strictly a drag racing engine but for all intents and purposes, let's say it is.

Top to bottom:
750 CFM Barry Grant VS carb.
RPM Air Gap (for Vortec heads).
RHS Pro Torker iron heads.


RHS AMS.jpg



.040" OEM block.
Wiseco PTS503A4 flat top piston, .014" down.
Elgin forged rods 5.7".
Factory forged crank (10/10). Nice fillet.
Compression ratio target is 10.25:1.
Cam spec: 280/280, 108 LSA on a 104 ICL. (Haven't dialed in the .050"-.200" numbers as of yet). Lift at ~.550".
Crower SS 1.6 ratio rockers.
COMP 26918 spring and tool steel retainers (or possibly PAC equivalent).
1 5/8" mid-length header with collector extensions (open exhaust).

Seems fairly average.
As stated the objective is for peak HP at ~5900 RPM.
I'd say HP and TQ will both fall in around 450 as seen on an engine dyno. Also hoping it's essentially flat for the rev range specified.
Does this look to be a doable undertaking? Specifically speaking, are the heads up to it?
This has been built virtually and for the most part also tested in the chassis with the exception of the cam and open headers.
I'm looking for opinions on the engine combo and not necessarily the car itself. Let's call it a DIY crate engine.
Sorting out the chassis will come later.

I think all will be good until you use that B/G vs the way the factory made it. I found this out back a few years ago when I ran the car and that BG vs dog sheet slow until I fixed it. I added the little brass pickup tube then the carb worked as good as my Holley HP vs. Seems some of these 750's just don't work right without that tube in there. I like the combo though.

[skinny z]

I think all will be good until you use that B/G vs the way the factory made it. I found this out back a few years ago when I ran the car and that BG vs dog sheet slow until I fixed it. I added the little brass pickup tube then the carb worked as good as my Holley HP vs. Seems some of these 750's just don't work right without that tube in there. I like the combo though.

There's a bit of history with this carb.
I'm the 2nd owner.
Originally purchased for the annular boosters to help tame a bigger cammed 350 it proved difficult to tune. It was further modified for screw in air bleeds. It did deliver decent highway MPG though which given that it was mostly street driven, was a good thing. It was never as fast as the QFT that eventually replaced it. Interestingly, the QFT missed the mark on MPG.
Then I bought that BG from my racing buddy and it worked like a charm on my 350. Same cam but different heads. I did approach the tune differently with the timing. Going from ported to manifold vacuum advance made a huge difference.
The engine gave up before I could dial it in for the track though but I did set a personal best with that same carb and a smaller cam.
And 20+ USMPG too.

As for the combo, as stated it's nothing extraordinary. This cam is smaller in comparison to the "bigger" cam in it earlier. That was 288/294 seat to seat intake, 236/242 @ .050", 110 LSA in at 104. Less overlap too. 71° vs 64°.
Still undecided on how to approach the .050" - .200" numbers. I'm not sure if 234 @ .050" with a .360" lobe (280 seat timing) is going to kill the valvetrain over the long haul. (The long haul being relative).

[Bill Chase]

Curious Kevin, for your stated goals why aren't you just getting a cast 3.75 crank and going to a 383. Cost of cleaning up and balancing a stock crank vs a new crank rough balanced to an 1800 gram bob weight the difference in price is insignificant. Instead of pushing 350/355 combos to the edge, why not enjoy the extra torque and horsepower at a lower rpm? Seems like you primarily want a street car that will run a respectable time at the track. As the saying goes no replacement for displacement.

[skinny z]

Hi Bill.
That was the plan. In fact, I had budgeted for an all forged 383 rotating assembly but with all that's happened in the last couple of years what with covid and the economy around here, the whole project was put on the back burner.
Fast forward to today and my quickest way back and least expensive, is to finish what I had started before a lifter set went south and wiped out the cam.

On the subject of crankshafts, I'd had that conversation with the shop and if my forged 3.48 stroke crank needed anything more than polishing, I'd go ahead with the first plan. As it turns out, aside from the needing to go 40 over, the rest is tip top so that kind of paved the way for a 357.

I won't be pushing this too hard. With a less than 6000 RPM redline, it should last a good long time. That is if my previous engines are any indication of what to expect.

As for what I'm after, it's always been street first then strip.
Now I'm starting to lean just a little the other way. In may be that it ends up at the track more often than around town or across the country.

[Elroy]

Well no matter what, it will certainly be the most discussed hypothetical engine build on speedtalk.

[skinny z]

Sadly, the hypothetical was all I had going.
And I thank everyone who's has entertained me with that discussion.
But now, as long as the machine shop doesn't go tits up in the meantime, the hypothetical is soon to become reality.

[skinny z]

Sadly, the hypothetical was all I had going.
And I thank everyone who's has entertained me with that discussion.
But now, as long as the machine shop doesn't go tits up in the meantime, the hypothetical is soon to become reality.

[BobbyB]

Can you post your expected torque curve?

[skinny z]

I can but remember, it's all hypothetical!

It'll be a bit before I can post up though. I'm not in the office.

[novadude]

Sounds really close to the "sledgehammer" Vortec build that Vizard did ~10 yrs ago.

https://www.motortrend.com/features/061 ... vy-engine/

[skinny z]

Sounds really close to the "sledgehammer" Vortec build that Vizard did ~10 yrs ago.

https://www.motortrend.com/features/061 ... vy-engine/

Very much so.
I modelled one of my Vortec headed 350's after that example about 10 years ago although I never had the cam spec dialed in.

One thing lacking in that article are the details regarding the cam. No seat to seat numbers IIRC.

This go around (#6?) is the same but different. The heads specifically.

[Elroy]

although I never had the cam spec dialed in.

How do you know when this is achieved? In a hypothetical world...

[skinny z]

although I never had the cam spec dialed in.

How do you know when this is achieved?

Not sure if I'm being tested or being asked a question.
I will say that I would have to try several cams and record the results.
Or, I can stand on the shoulders of those that have gone before me and use what they have found to produce the best results.
So, my having not having run a cam of the specification that's in the Sledgehammer article is an example of my not following brighter automotive minds than mine.

[Elroy]

Not sure if I'm being tested or being asked a question.

Your being tested . Good results are subjective at best. Even testing multiple cams to find the best one is in no way a guarantee that you have the best cam or are dialed in, just the best one that you tested. And im gonna take a stab that your going to be doing none of that(the reality part anyway). lol: But hey...Ill stay tuned for more of the faux, hypothetical, pseudo engine building. Continue.