Head bore size limit?

I have a 4.68 bore Premier block. I'd like to run a P51 head. Will I run into any problems there or will I have to go to an A460?

Thanks D... you sure are up early! but I knew that question would come out

my goal is big cubes (haven't decided on teh 4.3 or 4.5 sroke yet), but mild and streetable (small-ish cam) because it will definitely be driven on the street. 700-ish hp/tq and some mid-to-upper-6's in the 1/8th mile. This is in front of an AOD and rather low stall.....yes, kind of vague, but it's all in the planning stages at the moment and motor won't actually be built at least a year down the road.

I know it can easily be done with a smaller motor and stock block, but I got a good deal on this one and it gives me good potential if I want to go faster later.

That's the plan anyhow................................................................

IMO, That engine is WAY WAY overkill for the street. Save it for a good track build. A smaller inch combo imo would be alot more fun on the street.But thats just me. Good Luck man

Yes, but I think overkill isn't necessarily a bad thing when it comes to a block

No track-only builds in my future...this car will be my attempt at a good all around car. It's going to be similar to what Cobralcon did with his car, but a bit more drag oriented. A Drag Week type of thing.

I know...I opened up the can of worms with this one!

I Think it would be a pretty cool build to put those p-51's on that 4.68 bore ....... i know when we were doing my build the bore (4.560) we went with was right at the sweet spot , the unshrouding of the valves were better ....... i believe the flow potential of the p-51's would love to have a large bore !!!!!


get her done and put it on the dyno

bruno wrote:I Think it would be a pretty cool build to put those p-51's on that 4.68 bore ....... i know when we were doing my build the bore (4.560) we went with was right at the sweet spot , the unshrouding of the valves were better ....... i believe the flow potential of the p-51's would love to have a large bore !!!!!


get her done and put it on the dyno

Thanks, Nick. I hope so!

I guess to clarify a bit, this will go in a MII front end in a 65 Falcon. This is a pretty tight fit already and A460's being a physically larger head would create even less header clearance (I believe) They are also heavier on an already added weight on a small car. While not totally disregarding the A460's, I feel the P51's or similar would be more than adequate for what I want to do in the power department.

I am very curious about a build like this... and have similar thoughts about doing a big inch street motor.

while the HP potential of 620 inchs is way beyond the goal of this builld... is there NOTHING to be gained by the added cubic inches in a street type build? all things being equal... would a 466 have the SAME HP as a 557 as a 598 or in this case 620 inches? the gains may get smaller as you reach a point of saturation... but is it safe to assume that there will be SOME gains as you increas cubic inches without increasing cam, head or compression?

can you trade lower compression, smaller heads and smaller cam for more cubic inches to attain the same HP?

Shane

Are you going to try to run pump gas? That might be a problem getting the compression down with 619 inches. If you have it build it. Going up in cubic inches with everything else the same just builds power and torque at a lower rpm. With a hydraulic cam, just make sure you get it big enough to get the rpm where you want it. It will take a good bit more cam to make a 619 peak at 5500 than it would a 472.

The P-51's would work good with the hyd. cam because of the high flow numbers at .500 and .600 lift.

I don't know how in the crap you will ever hook that beast on the street though. But it sure would be fun trying.

It's your Monkey abuse him however you see fit.

Just make sure to keep us posted

I'll plan on running a 'street' solid roller, something with a pretty tight lash so it will rev enough. Wouldn't want to go much past 6000 though, if that. I definitely want to keep revs low for reliability and streetability. It will be EFI, as well.

I absolutely plan on pump gas and understand that a very pricey part of this motor will be the custom pistons...$$$

TorinoGT - I think we're on the same page. I've read plenty of builds on here with hp/tq #'s I like and running the approximate times I would like to be at with weight being relative, but the only thing is the stall speed is generally too high for what I want and camshaft too big. The big cubes I think will be able to run a lower stall speed and the camshafts to make the numbers will be milder and easier on the valvetrain.

At least that's the kind of stuff I've gleaned from this site (and the other)

I'll definitely keep all posted when the build starts, and on the car in general. The chassis work is just starting now.

TorinoGT wrote:

can you trade lower compression, smaller heads and smaller cam for more cubic inches to attain the same HP?

Shane

I don't think you can necessarily do that. To keep same hp levels you would keep the same heads/cam/intake but it would peak lower and likely seem more streetable. You would, however, gain more torque throughout the rpm range.

windsor wrote:
I don't think you can necessarily do that. To keep same hp levels you would keep the same heads/cam/intake but it would peak lower and likely seem more streetable. You would, however, gain more torque throughout the rpm range.

I know im over simplifying it... but to a degree... and gaining torque, and at a lower RPM seems like exactly what *I* would want for the street... I rarely get my garage built 466 above 4000 RPM on the street during typical stoplight racing... so 900+HP at 7000+ RPM really doesnt do me alot of good... I would trade that peak HP number, for a bigger number at a lower RPM...

then by all means, you need to stroke it!

To put it in perspective, we just did a 466 CID engine with a set of fully ported, rock & roll P-51 heads and made 750 Hp on BP 92 octane pump gas, at a true 11.5:1 compression ratio. It also had a fully ported Weiand tunnel ram manifold and two carbs. That's 1.61 Hp per cubic inch, so just multiplying that number by however many CID you are going to be, shows you the potential. Assuming that you will not run a Weiand tunnel ram, then you can knock about 60-70 Hp off the deal.

Lem, and I know they work really good on Randy Moore's 562 CID race engine @ 951 Hp, but as to where the upside CID limit is,,,,,,,, I haven't seen that engine yet. I don't know that I would go much bigger than a 598, but that's an educated guess on my part.

Hope this helps,

Charlie

oh come on guys, don't kill my dream with logic, common sense, and experience!

Honestly, I think one of the builds that would suit my goals most is something like Greg's (yellow Torino) with his 545. Better heads but smaller-but-roller cam though. I may use the 4.3 crank for 590 cubes instead of 620 w/4.5...

But, glad to know the P-51's will work on the bore, now that we've come full circle.

windsor wrote:oh come on guys, don't kill my dream with logic, common sense, and experience!

Honestly, I think one of the builds that would suit my goals most is something like Greg's (yellow Torino) with his 545. Better heads but smaller-but-roller cam though. I may use the 4.3 crank for 590 cubes instead of 620 w/4.5...

But, glad to know the P-51's will work on the bore, now that we've come full circle.

I know im the opposite of an expert... but I say go big... I dont see any reason NOT to go with a 4.5 inch stroke... sure the gains might diminish... but there WILL be gains... and as for the whole "you gotta put that to the ground" talk... that will be your next project.. a suspension to handle the power... and nobody says you have to put your foot to the floor every time you leave a light either!

I guess the big question, is can you keep the compression down with that stroke, bore and head combination?

I envy the idea of a huge inch street (pump gas) motor... sure it wont be all it could be... but everyone is aware that you DONT want 15:1, .900 lift, sheetmetal intake blah blah...

Shane

Yeah, every combo is a compromise of some kind. My chassis is actually being done now and will be adequate, I think. Motor is well down the road, but I was just wondering about the big bore on the stock-type heads.

Compression shouldn't be an issue, I may run a 6.7 rod if needed...no biggie on that issue.

As for not being able to use that on the street...I have no plans to. Cruises, shows, and to and from the strip is all I will do. I used to street race about 15 years ago, but no more. Being in law enforcement, I don't think it's such a good idea

c.evans wrote:Assuming that you will not run a Weiand tunnel ram, then you can knock about 60-70 Hp off the deal.

dfree383 wrote:I also don't think the tr was worth that much over the single 4, maybe 30 hp on top.

Mmm, Charlie builds an engine, dynos it, and Professor Freeloader doesn't think Charlie is right? Mmm.



Dave

Well, If uncle Charlie keeps hanging out here, he'll catch a few pointers from the dreamer crowd.

i dream non-stop

DJOHAGIN wrote:

c.evans wrote:Assuming that you will not run a Weiand tunnel ram, then you can knock about 60-70 Hp off the deal.

dfree383 wrote:I also don't think the tr was worth that much over the single 4, maybe 30 hp on top.

Mmm, Charlie builds an engine, dynos it, and Professor Freeloader doesn't think Charlie is right? Mmm.



Dave

Dave,

It was an engine we did together, so give Dave Freelander some credit. It was an "alternate" engine for the EMC contest and after a lot of blood, sweat and tears here in Owensboro working on the thing, with 70 some odd dyno pulls, then hauling it to the contest in Lima,,,,,we did NOT get to dyno it,,,,,which really fried my azz.

Anyway, the shortblock was rather generic as Freelander has described elsewhere. In all of the dyno pulls we had the Weiand tunnel ram on it, so we are both just expressing an opinion as to how much the 2 X 4 set-up is worth verses a single plane Victor. Likewise at the contest, the majority of the carbed engines had a 2 X 4 tunnel ram set-up.

The weekend that it made 750 Hp was when Lem, Dave and Mike were tuning on it. I was out of town. However, the 750 Hp tune was not the one that produced the best average score. Smaller headers that choked the HP peak by about 12-15 Hp, but helped raise the low end torque curve a bunch,(there was a torque dip that we tried to get out of it) was the one that produced the best overall average score. Remember the pulls were made form 3,000 to 7,000 rpm, and then the torque average and the horsepower average are added together.

Hope this helps,

Charlie

Guys,

I know I said knock off 60-70 Hp for not using the tunnel ram,,,,and I was just trying to point out to Windsor, that even if you knocked off that much, a P-51 headed 632 CID engine (as he mentioned) would still be a monster.

Anyway, at the 700 Hp level, a Weiand tunnel ram is NOT worth 60-70 Hp over a single plane Victor, it would be much, much closer to the 30 Hp that Freelander mentioned. I'm sorry for the mistake or confusion.

Charlie