I am running a 70 Boss 302 in my 72 Comet GT I am tired of mixing fuel to drive it. 11.45 to 1 just wont run on pump gas. I am looking at a set of Pro Comp aluminum heads for a 351C Boss engine. They are 64cc instead of the 58cc cast boss heads. It should drop compression to 10.2 to 1 should run on 91 octane. Has anyone run a set of these heads? If so did you like them, problems? Thanks Dennis in Iowa
I don't have any personal experience with pro comps, but I've heard if you buy them bare and assemble with good valve train parts they're a decent head. I had looked into a set a while back for a sbf, google search showed many valve, and valve spring failures and for the cost of the valve train and machine work it was more cost effective to start with a better head(trick flow).
I read that they won't even make equivalent power to a set of un ported iron 4V heads. A bad copy of a CHI Australian head seems to be the consensus. TFS makes a nice Cleveland head that flows pretty well. I have looked at them closely at Summit and the castings and machine work are pretty good. If I were going street Cleveland, I would choose an AFD, CHI or Trick Flow head and forget about the Pro Comp stuff. Your car is awesome and would be a lot more drivable with a set of the aforementioned heads. The 2V sized intake ports and improved exhaust ports would work much better than the large port Boss heads on the street. The aluminum heads would also tolerate more static compression and allow you to make as good or better power with less ignition timing. Just 2 cents from a person that has owned a lot of Clevelands in addition to a Boss 302 Mustang.
Cant say about the boss but...I have 10.3 comp ratio in my 302 mav with cast iron 58 cc heads and 10.5 with the 351 in my sprint. Both cars run quite well on 91 octane pump gas. Good ignition system and optimized timing along with a proper carb tune should allow you to run 11:1 on pump gas with no issues. So yeah, you should be fine W/ 10.2:1. Piston quench/chamber shape etc...Do factor into how tolerant the engine is octane wise too. I would stay away from anything that is pro comp...
i ran trick flow heads on my 66 impala for years, loved them. I installed trick flows in my comet, and great so far, if I can get all the gremlins out of my car to really drive it. taking a vacation and then hitting it hard and get it running. I would stay away from the pro comp. find your self some trick flows or edelbrock, or afr. worth the money on good valve train parts.
if you treat those bare castings as they should be treated(bare chunks of aluminum) and spec your own parts they are not so bad. TONS of big name shops have come out with CNC versions for them as well simply because some people think they are saving money and the market is there to justify creating the CNC file from a hand ported casting. Dan is right as most builders and shops will tell you straight out that they will not match the power of a more expensive and well designed castings right out of the box(and sometimes even after mild porting has been done too). Those heads will be down in power across the board and you will need more cam than most other heads to even get close to the better designed castings. This is also true of the iron Cleveland heads as well. BUT.. despite them having improved the quality control.. they still need to be checked out for geometry issues and some builders have also reported that they are also "too soft". The Procomp name has been so tarnished with bad press that they actually changed their name to Speedmaster now(as of last year). For most savvy buyers, that should be enough of a hint right there. As for the CR concerns?.. I would not stray away from compression with an AL head(any casting) since they are much more tolerant compared to the iron Cleveland stuff. The chambers alone on today's more modern head designs will easily allow another point and half jump from where an old outdated iron head would be getting into trouble. Plus these cars are light and you likely have plenty of gear to avoid lugging the engine enough to detonate it anyways. If you are detonating?(or the tune has to be changed considerably for higher ambient temps?).. then you surely have some tuning issues to iron out and aluminum castings from any cylinder head mfgr won't completely save you there. Chamber designs and quench area/height aside.. cranking compression is a very good indicator of an engines potential octane tolerance and the ignition curve needs to match that. For any street motor I build these days.. I try hard not to fall much below 200 psi. Makes for a more responsive motor that comes up "on the pipe" quicker.. higher manifold vacuum created from higher compression also helps the boosters come on quicker and allows more precise fuel curve tuning.. that inevitably helps the motor come up on the cam quicker and is considerably funner to drive. Incidentally, all of those things can actually IMPROVE an engines octane tolerance despite the higher cranking and dynamic compression ratio. The fuel octane rating is only part of the whole picture and I try to run 11:1+ whenever possible. My newest motor will be closer to 12:1 and will initially be tuned to run on pump gas before moving to an E85 mix and much more aggressive timing curve(not to be confused with the total timing number). Great stuff for compression motors(I know guys running 13:1 on the streets) and you might want to check into that as well if E85 is widely available to you. Plus, you won't even need to do the full alcohol carb conversion with mixes below 50/50 either. The mechanical fuel pumps diaphragm may not last as long but there are other "alcohol compliant" alternatives available there nowadays too. Also consider the affect that a good cylinder head has on the engines camshaft requirement as well. The iron Cleveland head needs an entirely different cam design than the newer AL stuff would(even with knockoff heads like these although to somewhat lessor degree) for best results. The better the castings low-mid lift flow along intake/exhaust flow differential is.. the less overlap and duration would be required to make the same power. If the static compression ratio is lowered on an already cam compromised combo of parts(too big for the CID and/or where the cam has already bled off too much static compression to give cranking pressures of 170psi or lower).. the engine will be even softer in the lower rev ranges and take longer to come up on the cam unless you add more gear to help compensate for the shortcoming. And for god's sake man,(used in vain here because I can't stress this enough).. stay away from EFI style cams with wider lobe separation angles/LSA (higher than about 110 degrees LSA). Narrower LSA grinds will also bleed some pressure off the cranking compression as well but the extra scavenging potential from the additional overlap will pick up the larg'ish intake port(for 302 cubes anyways) and help fatten the mid-range to improve average power under the curve. Wider LSA's with drops in static compression ratio's will really soften the motor up(ESPECIALLY smaller shorter stroke combo's like this) and should be avoided at all costs unless all you care about is idle quality and fuel efficiency. PS. not to knock the Edelbrock fans here.. but those are also economy heads with potential for machining and core shift issues(talked with many builders/some of which who are world renowned and have also witnessed with my own eyes).. and they also use profit improving components on those heads as well. When it comes to economy style heads.. it's always best to spend the extra bit of cash on bare castings and spec your own parts. This is what makes the better AFR and Trickflow castings more relevant from a total investment standpoint after everything gets tallied up at the end of the build.
All good stuff, but let's not forget that the question is focused on CLEVELAND heads. AFR does not even produce them. Discounting the Glidden SC1's, the Edelbrock street Cleveland head is a pretty dated design. I would pass on these and go with the TFS 190's for a street Boss. The castings are good/great, they make good intakes for them and they are made in the USA. The Aussie stuff, AFD and CHI, are real good as well, but pricey. Let someone else sort through piles of Pro Comp castings to find a good one.
groberts, you have a wealth of knowledge and the fact that you freely share it here is greatly appreciated. So many people hold what they know tight and aren't willing to share, thanks for the education.
Last summer I sold a pair of 210 cc ProComps that a friend gave me after he bought new AFR's. The ProComp's intake port alignment was so far off he had to turn the intake gaskets upside down to get them to seal.
Thank you very much, sir. I'm very grateful for the ones around here who freely share info and just paying it forward the best way I know how to, bud. Always been blunt and from the hip by nature and some guys are put off by my spouting and regurgitation of engine building theory. They too quickly assume that I'm trying to appear "holier than thou" or climbing up a taller pedestal but in the end.. I do it because I wish I could have more often received the consolidated version many years ago. I struggled hard to understand just the little bit that I do these days and back then(before the internet) many/most people wouldn't willingly share much at all because it gave them a bigger advantage on the competition, street, track, or otherwise. You had to be slick enough to mine the info from their brains without asking questions for fear they would shut the door in your face after fully realizing what you were doing.. and also have good eyes to pick up on the subtle differences in parts config's for the more competitive combo's. Nowadays, the WWW has everything I've ever learned over an entire lifetime and much much more spread all over the place. Unfortunately for most(myself included), knowing something is one thing.. but learning when to apply it is an entirely different issue altogether. Which is why I tend to bother world class builders, racers, and designers/engineers whenever they have time to talk or chat with me. The rest of the time I just follow them and get drug around the internet while hanging tightly onto their coattails. Pride and ego aren't very conducive to the learning process and only cause issues in the long run.
Still very curious as to what this OP's engine makes for cranking compression in its current configuration? PS. on the reread.. I just noticed the "11.45 to 1" SCR number he mentioned. Something does not compute and I'm curious as to how that's even possible on 302 cubic inches without pop-up pistons. Have to know where you're coming from to better understand where you'll end up. Plus, 64cc chambered heads are way too big for a larger intake port(even the 2V port versions) on such a little motor and compression is the only thing that can pick that port up short of too small a camshaft being used to crutch it. Motor will be softer everywhere but especially at lower rpm's/airflow and expected powerbands have everything to do with intake port velocity requirements. Dual plane manifolds will help crutch too big a port(for this CID) as well.. but applying too many band-aids onto the same cut won't heal it any faster if you catch my drift here.
I hear you, I remember hanging out at a local parts store in high school, it was the closest thing we had to a speed shop. The guys ranged from good natured and helpful to outright butt heads. Some shared a little while other just razzed us. Great memories regardless and all that hanging around eventually landed me a job there. Still don't know as much as I would like to but I have enough to get myself into trouble!
Seems to me if it were my car I would rig up a some sort of progressive methanol injection and do a 50/50 mix. I guess you're still technically mixing fuel. Probably less cost and work than swapping heads. Or am I way out in my thinking?
