Yes another cam thread - Pontiac GTO Forum
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post #1 of 6 (permalink) Old 07-01-2014, 12:15 AM Thread Starter
 
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Yes another cam thread

Hey guys,

So I'm thinking of changing up my 461 build a little bit. The main part I'm working on now is the camshaft.

I want my transmission to be fully engaged cruising the highway at 70mph. My semi stock 400 (411 bored 60 over) was 70mph @ 2100rpm.

I got a recommendation from a reputable shop and this is what they suggest:

Comp Cam hydraulic roller custom grind
276/282 @ .050 224/230 .553/.561 on a 112 lobe separation.
2000rpm stall

This is for a street only car with these specs running on 92 octane:

Auto transmission
3.36 gears
461 stroker kit
Mahle flat top pistons
Heavy duty oil pump
KRE aluminum D-port heads 85cc 2.11/1.66 valves, ported to 310cfm
KRE northwind intake port matched 310cfm
Holley 4150 1000cfm
1.65 roller rockers
compression ration appox. 10.6:1
Ram air resto d-port manifolds
2.5" pypes with race pro mufflers
2000rpm stall converter

Just checking if this is a decent cam recommendation? ...what kind of hp should I see?

Thanks.
-Norm
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post #2 of 6 (permalink) Old 07-01-2014, 05:48 PM
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Is this a running engine that you're thinking of changing? (and if so, what cam is in it now?) or a fresh build?

If you've got power brakes you can't go too rowdy on the cam without messing them up (or having to either add a hydroboost system or a vacuum pump). Overlap is what kills vacuum. The hydraulic roller you've listed sounds pretty safe with those .050 duration figures and the 112 LSA, also the fact that it's a roller profile helps keep overlap down. If it helps, I'm running a solid roller in my car, 236/242 @ .050 on a 110 LSA, and I'm running hydroboost brakes. You'd probably be relatively safe in the "range" between what you're thinking and what I'm running.

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post #3 of 6 (permalink) Old 07-03-2014, 01:12 AM Thread Starter
 
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Fresh build.

I figure I need to go max stall of 2000rpm to keep trans from slipping on highway. I don't want to rebuild trans yet or build hydro boost system at this time.

How well do the add on vacuum canisters work? I think that just adds to the size of the reservoir with check valve I believe.

Messed around with desktop dyno 2000, if my calculations are correct I think I can get about 500hp out of it with the more mild cam from above.

-norm
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post #4 of 6 (permalink) Old 07-03-2014, 12:32 PM
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Be very careful with those simulators. It's very easy and tempting to set them up so that they are overly optimistic. I use Performance Trends Engine Analyzer Plus myself, and it happened to me. When I actually ran the engine on the dyno it wasn't as good as what had been predicted. However when I changed the "running conditions" settings (the settings having to do with atmospheric conditions and related) to the most "pessimistic" options then the simulator was extremely close to what it actually did on the dyno.

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post #5 of 6 (permalink) Old 07-03-2014, 05:07 PM
 
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Quote:
Originally Posted by Norms68 View Post
Fresh build.

I figure I need to go max stall of 2000rpm to keep trans from slipping on highway. I don't want to rebuild trans yet or build hydro boost system at this time.


-norm

Why not look into a factory TH-400 "switch-pitch" converter conversion? They have been around since the 1950's. I had one in my 1954 Buick and when it dropped down into the higher stall mode, it was like a kick in the pants and that was with a 322CI engine. I recall my 1955 Packard has this also as a "variable-pitch" converter.

"The torque multiplication is 30% greater at stall in high stall than low stall (2.6 fold vs 2.0 fold). It makes it damn near impossible to hook up a healthy big or small block engine even with street gears without some very sticky tires. However the slip at all engine speeds in high stall is much greater and for best results it is best to leave high stall around 2/3 to 3/4 way through 1st gear. The launch is dramatically improved if you can hook up.

A car with 2.93 gears will accelerate from a standstill like the same car with 3.42-3.55 gears and a fixed pitch converter matching the stall speed of the lower stall setting of the variable pitch. Therefore you can sort of use it as a poor mans over-drive, gear the car higher and let the converter in high stall make up for the lack of a low first gear. If you switch back to low stall towards the end of 1st gear you'll be able to stay in first gear longer as the rpm's will drop 500 due to the converter tightening up. There is some information in the book How to Work With and Modify The Turbo 400 Transmission by Ron Sessions. 10 Years ago Kenne-Bell sold lots of variable pitch parts plus had lots of free info on them. I'm not sure if he still does or not, he seems to have moved more to the mustang market now."

The Buick guys use these a lot on their big 455CI builds with good results. Do a web search and you will find suppliers -just something to think about.
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post #6 of 6 (permalink) Old 07-13-2014, 01:02 AM Thread Starter
 
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So i decided to go strictly street on my build. Changing it up a little from original plans.

Little less heads, carb, intake and chatted with Jim Butler a bit.

We decided on a Comp Cams custom grind with following specs:

Hyd roller cam 282/288 @ .050 230/236 .510/.521 112 lobe separation.

Also going with about a 2000-2200 stall so I wont be slipping the trans at 70mph highway speeds.

Thanks for the help.
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