Pontiac GTO Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
1,611 Posts
What octane pump fuel do you have avail? Is 420 gross HP/500 ft lbs of torque at the flywheel with iron heads in the target range, or are you one of the guys that believes he needs 500hp at the rear tires? The latter is a much more expensive endeavor.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #3
93 octane,
Here's what I got
6x4 iron heads/ ported.(97 cc)
1974 400 cid
Eagle 461 stroker kit with cast crank
Performer intake manifold
650 Holley ( prob too small)

And yes I am realistic about my expectations
 

·
Super Moderator
Joined
·
5,744 Posts
Couple questions...

What's the casting number on that 400? (passenger side rear of the block, below the deck, on the transmission mount area).

Yeah, 650 is going to be a little small. if you want to stay with that manifold and a square bore carb, you're probably going to want at least 800 if not a tad more. Check out AED, Quickfuel, or Demon.

With 97 cc iron heads (you did actually measure them, right?), flat top pistons (which usually have 6 cc's in the valve pockets), factory .045 (compressed) gaskets, and zero-decking the block (which I strongly recommend) you'll be at 9.358:1 --- dang near perfect for what you're building.

What are you thinking about for the rest of the valve train?

Recommend you get yourself a copy of Jim Hand's book, or the more recent one by Rocky Rotella (or both) for some more good tips on prepping your short block.

Holler if we can help more.

Bear
 

·
Registered
Joined
·
13 Posts
Discussion Starter #5
its the good casting number 4xxxxx, not the 5xxxxxx thinner block.
car is 1970 lemans
valve train is a ? need advice on cam( a little mean, but NOT a track cam)
car has 3.42 12 bolt posi
m21 munci
and yes i actually checked the cc's of each chamber with a kids medical . that's what gave me the 97 cc
 

·
Super Moderator
Joined
·
5,744 Posts
Power brakes? Any other accessories that might be sensitive to idle vacuum?

And the most important question: Budget. Considering all the horror stories I hear about people having problems with flat tappet valve trains these days, either due to low/no ZDDP in the oil to questionable metallurgy of the parts, the only way I'd recommend a flat tappet system over a roller would be if there were big concerns about cost. Rollers are quite a bit more expensive though. I'm running a solid roller in my 69, and I like it. With the way I drive the car, and how much I drive it - I tend to adjust the valves about twice a year, and I've never found them to be significantly "out" when I do. I even went to the extra trouble of installing oil restrictors in the lifter bores and all that. The cam profile I have has a little attitude, but it's not overly aggressive. Being a roller profile helps with that because the ramps, being steeper, allow more duration without forcing you into a lot of overlap - and it's overlap that affects streetability the most. At the time I built my engine, I chose mechanical over hydraulic due to the significant weight difference between solid and hydraulic roller lifters. If that's still the case, I don't know.
The cam I have has 236/242 degrees duration at .050 lift, LSA of 110, and it's installed at 106. Lift at the valves with 1.65 rockers is just a taste over .600. You can hear what it sounds like here:


That's about a 550 rpm idle.

Is that close to what you're looking for?

Bear
 

·
Registered
Joined
·
345 Posts
Starting my 461 build any tips.
My goal is a very street able motor with little or no track time
93 octane,
Here's what I got
6x4 iron heads/ ported.(97 cc)
1974 400 cid
Eagle 461 stroker kit with cast crank
Performer intake manifold
650 Holley ( prob too small)

And yes I am realistic about my expectations
I'll make a few comments, because that's what we do on forums. :smile3:

The Performer intake, as well as the 650 will choke a 461. I'd recommend a good 800 Q-jet, like maybe an SMI stage 2.

http://www.smicarburetor.com/products/sfID1/28/sfID2/9/sfID3/100

But, if you prefer a square bore, most consider the downleg booster type carbs, better than the cheaper straight leg type. If your budget is limited, I think the cheapest decent carb of this type is the old Holley 3310-1 that most call a "780 vacuum". There are still some of these around. Ebay usually has several used and rebuilds.

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2051541.m570.l1313.TR5.TRC0.A0.H1.Xholley+3310-1.TRS0&_nkw=holley+3310-1&_sacat=6000

If you have $500 to spend on new carb, Quick Fuel makes some nice vac sec street carbs.

http://www.amazon.com/Quick-Fuel-Technology-SS-780-VS-Carburetor/dp/B003M96BHW

Some guys insist on a double pumper. But, I & many others prefer the vac secondary type. The last bracket car I bought had a 750 straight leg vac sec Holley. I figured I'd probably swap it out for a Q-jet. But it worked so good, I just kept it on there. No, the car was not quick at all, by today's standards. Ran 7.30's in the 1/8 mile. But, the carb, on a Torker 2 intake, left clean either from an idle, or a 2000rpm power brake--1.60's 60ft times. This was with 4.10 gears, slicks, and ladder bars.

So, the engine was probably making around 400hp or a little more & about 500ft lbs of torque. On the street, with hard street tires, the main problem with this engine would be traction. I just don't see why anybody would really NEED any more power than 400hp/500ft lbs. But, whatever.

The single plane intake is just fine for a 455+. If you want a single plane which will accept a square bore or Q-jet, one of the cheap Chinese intakes will work. They sell for about $150 on Ebay. I bought one. It actually looks real good to me. Haven't used it yet. Will probably save it for use with a Q-jet.

http://www.ebay.com/itm/Pontiac-326-350-389-400-421-428-455-Shootout-Intake-Manifold-Satin-/181603301013?fits=Make:Pontiac&hash=item2a48667695:g:Ni4AAOSwg3FUgQLF&vxp=mtr

http://www.ebay.com/itm/PONTIAC-326-389-400-455-V8-Aluminum-Intake-Manifold-Air-Gap-3000-7500-RPM-/331084137172?hash=item4d162702d4:g:IZwAAOSwq7JUIuG9&vxp=mtr

Now, about the cam. I've done some price checking on all the parts for a complete roller cam set-up. The bottom line is that the roller will cost over $1000 more than a decent HFT set-up. The HFT will easily make a very streetable 400hp/500ft lbs. And, if you use either Hylift-Johnson 951R or Rhoads lifters(which are modified Hylift-Johnson), you are not likely to have any cam failure issues. Obviously, you need to use oil with sufficient amounts of ZDDP, or oil supplements with it, and follow proper break-in procedures. Lots of guys use the 15W-40 diesel grade oils, like Rotella T & Delo 400. I'm using Delo 400 & one bottle of STP, which contains ZDDP.

As for specific cam recommendations, they can vary WIDELY on the forums, depending on who you ask. So, I'll just post my thoughts and not argue with others. If you have power brakes, I'd use an 041 clone such as the Crower 60919 or Melling SPC-8, and Rhoads RL-9518 lifters.

http://www.ebay.com/itm/Engine-Camshaft-Stock-MELLING-SPC-8-fits-68-70-Pontiac-Firebird-6-6L-V8-/131527250214?hash=item1e9fa29126:g:~WEAAOSw-vlVjneN&vxp=mtr

http://www.summitracing.com/parts/rhl-9518/overview/make/pontiac

If you don't have power brakes and want a little rougher idle, you can run the Hylift-Johnson 951R lifters. Paul Knippen is a Pontiac engine builder who sells these lifters.

https://www.facebook.com/PaulKnippensMuscleMotors/

There are certainly bigger cams you can choose, if you just want a nasty idle. But, these 041 clones are proven in 455 street Pontiacs. They will make lots of low end torque, and will pull to 5000rpm--just what most need for the street. IMO :smile3:
 

·
Registered
Joined
·
13 Posts
Discussion Starter #9
yes power brakes , a/c car.
my budget is not unlimited, I would like to save money where I can and spend it where I need it. this motor will not need to be beat on very often. I assume its going to be alot more fun than the small valve 350 i have in there now.
 

·
Super Moderator
Joined
·
5,744 Posts
yes power brakes , a/c car.
my budget is not unlimited, I would like to save money where I can and spend it where I need it. this motor will not need to be beat on very often. I assume its going to be alot more fun than the small valve 350 i have in there now.
Ok then, that helps. My car makes about 12" of vacuum at idle, which in my opinion (YMMV) would be marginal for power brakes. That's why I chose to convert to hydroboost during the build. You're going to want to pay very close attention to the overlap spec on the cam because that is what affects idle quality and idle vacuum the most. Overlap (you probably already know) comes from the combination of how aggressive the opening/closing ramps are, the lift duration, and the lobe separation angle (LSA) of the cam. If you decide to go with a flat tappet valve train (they definitely are less expensive) then you won't be able to run as much duration as you would be able to with a roller because the ramps can't be as steep as they can be with a roller. The 041 profile oldskool mentioned might be pretty good for you, combined with a set of controlled leakdown lifters (such as the Rhoads). That cam is pretty nasty in a 400, but in a 461 it would be a lot tamer - and the lifters help with that even more. Like everything else that involves these cars, you'll find opinions all over the map with regard to that type of lifter. Some love them, some hate them. I've never run them myself so I can't offer any first-hand knowledge. I "hear" they can be noisy, which by itself wouldn't bother me personally in the least, but I might be concerned about the effects of the 'hammering' that causes that noise in a system that wasn't designed for it (i.e. valves shutting harder than usual due to them closing while the lifter is still on the steep part of the cam, because of the leakdown effect at low rpm) --- but that's just Bear thinking out loud - I really have no direct experience. You can also tame overlap some by going with a wider LSA cam, and at 9.3:1 compression you should be pretty safe doing that. (Wider LSA's tend to build more cylinder pressure which can in some cases get into trouble with detonation).

Something you might consider if you're interested in such things, is licensing yourself a copy of the Performance Trends Engine Analyzer. That's what I did (I got the 'plus' version). It allows you to build a model of your engine (the more accurate measurements you have, the better) and then you can play around with different cam profiles, installations, "and stuff" to get a feel for what the end results would be. Once I got my inputs and settings right, it was scary-close to what my engine actually made on the dyno during break in. It's not a free program, but it's sure a heckuva lot cheaper than experimenting by swapping out parts. :wink3:

Bear
 

·
Registered
Joined
·
345 Posts
041/Rhoads

"...The 041 profile oldskool mentioned might be pretty good for you, combined with a set of controlled leakdown lifters (such as the Rhoads). That cam is pretty nasty in a 400, but in a 461 it would be a lot tamer - and the lifters help with that even more. Like everything else that involves these cars, you'll find opinions all over the map with regard to that type of lifter. Some love them, some hate them. I've never run them myself so I can't offer any first-hand knowledge. I "hear" they can be noisy, which by itself wouldn't bother me personally in the least, but I might be concerned about the effects of the 'hammering' that causes that noise in a system that wasn't designed for it (i.e. valves shutting harder than usual due to them closing while the lifter is still on the steep part of the cam, because of the leakdown effect at low rpm) --- but that's just Bear thinking out loud - I really have no direct experience..."


Ever since I had a stock type lifter come apart at a race(The paperclip retainer came out, dumping the guts in the lifter valley.), I've used nothing but Rhoads lifters. Can't remember how many 455 bracket engines I've built(but more than 6). I used Rhoads in every one. Never had one single problem with any of 'em. They all had high comp factory heads, with factory valves. Never broke a valve or had any valve problems.

Most of these engines had an 041 clone cam. With the 041/Rhoads the engines would idle smooth below 1000 rpm. I set 'em up to launch from an 800rpm idle, with a 750 Q-jet. And that was with TH400 trans & stock 13" converter. This combo left quick, producing low RT's and lots of wins. We shifted at 5000rpm, with a rev limiter set on 5500. So, stock rods were safe. Never broke one, in a 455.

Now, of course, 455's can use more cam. When running a 1000ft track, we needed a little better ET's to run a higher bracket. So, I went to a CC cam with 244/253 dur @ .050 lift, and 4.88 gears. The car went from 10-teens to a 9.85. And it would continue to pull passed 5000rpm, with no problem. But, for street use, I'd use and recommend the 041/Rhoads combo. Is it PERFECT for everyone ? NO ! But, it's just hard to beat. IMO :smile3:

http://forums.maxperformanceinc.com/forums/showpost.php?p=5455448&postcount=98

http://community.fortunecity.ws/silverstone/pontiac/101/build/cams.htm
 

·
Registered
Joined
·
13 Posts
Discussion Starter #13
Thank you so much, both of you, I'll I need to do know is survive my machine shop bills, get the block and heads back , order parts and get wrenching
 

·
Premium Member
Joined
·
776 Posts
Wishing you good luck with your build. I've been thinking about doing one myself and I found this really helpful link on the PY forum (if you haven't already seen it). The guy doing the stroker build gets lots of advice from those who've done it and the OP posts photos as his build proceeds.

Here is the link:

Need Recipe for Streetable Budget 455 Build - Page 11 - PY Online Forums

(I put up page 11 first as their system puts the beginning at the end:surprise:)
 
1 - 14 of 14 Posts
Top