Trev Vaa 1,185 Posted March 31, 2014 no closed chamber i would assume, need dome top pistons to get that compression on open chamber heads. 11:1 is plenty of compression for that cam either way. yes more compression will make it more responsive. but it will not make up for the fact the ports are huge, they are about half an inch in diameter wider, and a bit taller too. thats on the intake, which is what causes the issue low end torque/hp loss. i take it yours were oc 4v heads then yeah ? we are kind of getting off topic either way.... we can open another topic for 2v vs 4v, but the discussion has been had a hundred times. Share this post Link to post Share on other sites
blownxd393 25 Posted March 31, 2014 Sorry to go off track. Just wanted to know more bout your 378ci combo and your personal experience but you are quite vage ? This info is to help the guy asking the opening questions, can't see why its not all revelent. After all he's building an old school 378ci and I've done 1 or 2 in the past LOL. Carry on.....I could talk all day but if you would like me to butt out I will. Cheers Carl Share this post Link to post Share on other sites
Trev Vaa 1,185 Posted March 31, 2014 sorry bud, not my engine, don't know all the details about it, just the basics, can find out more about it, send me a PM if you like we can go from there. Share this post Link to post Share on other sites
Fordon 351 69 Posted March 31, 2014 Theres a bloke in Welshpool calld nozzteck all he duz is crank grinding 1 Trev Vaa reacted to this Share this post Link to post Share on other sites
blownxd393 25 Posted April 1, 2014 the reason i asked, no closed chamber i would assume, need dome top pistons to get that compression on open chamber heads. 11:1 is plenty of compression for that cam either way. i cc'd a set of old open chamber 4v heads i have on shelf and they are 65cc but in your defence some has been milled off mine i would say. bore-4.030 stroke-3.7 my oc 4v heads 65cc generic heads gasket -.040tho gasket bore-4.080 deck-0 flat top trw pistion valve reliefs and ring rail - 3cc 11.1 to 1 comp in my opinion 11 to 1 isnt plenty for this cam but it would do ok imho. bore Share this post Link to post Share on other sites
Trev Vaa 1,185 Posted April 1, 2014 yeah you're right, they've defintiely been milled, standard OC heads are 75cc. however, milled 4v OC heads do provide better quench area than closed chamber, leading to less detonation and better performance etc milled OCs would be the way to go, although does mean milling intake to suit + whatever you already have to take off for decking the block to 0. closed chamber is around 63cc factory. i've CC'd both 2v and 4v open and closed chamber, Martini heads does my work. theres 71 degrees of overlap on an f246 (just looked in my camcard specs), cant run much more than 11:1 on pulp with cast iron heads with this cam. not unless you want to sacrifice timing in summer, it doesn't bleed off enough compression. of course if you went e85, 12.8:1 would be a walk in the park. either way, 11:1 is PLENTY for this cam to make it work properly. again, this is off topic so please, either PM me or open another topic to debate 2v or 4v. its an ancient topic and i would also avoid comparing home ported heads without flow results to ported heads with flow results. i am not in any way knocking your work, but that is like comparing apples and oranges. i know for a fact my heads will support 505hp with ease. just like i know for a fact 4v heads are boggy (no torque or hp) under 3500rpm, there simply isn't enough airspeed in the port. raising the port floor helps this issue immensely. but again, why bother. the heads are $800 on their own, then you have to do/spend $600 + valves or do a lot of work to get them to a benchmark, rather than getting a set of heads for $50 and spending $1000 all up on them + valves and they match this combo perfectly. and will still be more driveable than the modified 4v's. if i were honest, i would say it seems you think in an oldschool way, which is cool, just outdated. this will be my last post on this particular topic of 2v vs 4v in this thread. btw i have owned both 2v and 4v headed engines, and driven and built plenty of both and plenty of alloy headed clevelands, windsors and big blocks. (of which i can give you every detail i have written down and it includes an f246 351c in there too) if it were my personal engine, with the money you were spending, i would go AFD 2v's, AFD intake, and probably pick another cam that's up to date with current heads, like a camtech CT2021-478-110 if you were fine running a solid roller (insanely torquey and extremely well performing for its size), or if you wanted maintenance free a CT2021-49904-110 hydraulic roller (perform about as well as the f246). again around the 11:1 comp (could go 11.5 with the alloys if you wanted though) its worth spending the extra money on the heads n cam. would also reccomend a pavtek girdle, good insurance for a few hundred $$$ if you want to stick with what you have spend the money on 2v's. Share this post Link to post Share on other sites
blownxd393 25 Posted April 1, 2014 Man.....you think I go off track (jokes) Please explain to me how milled oc have better quench then a set of cc heads ? Can't be bothered starting a new thread. Please keep it simple. For your info yes iam very old school and I love my cc heads. Share this post Link to post Share on other sites
Trev Vaa 1,185 Posted April 1, 2014 yeah no worries bud sent you a PM we'll leave this thread instead of cramming it up more than we have didn't realize how long my last post was either. shiiiiiiiit lol Share this post Link to post Share on other sites
noddy 451 Posted May 18, 2014 hey hey i just threw a 40 tho out chev rod combo flat tops zero deck height in mine with over bore be a 380 or close enough with 302 closed chamber heads 9 yes i know the comp will be right up there dosent hurt to try) have no idea on the cam in mine its a low mid range towing cam unknown specs but know reading this i may re think to something else Share this post Link to post Share on other sites
