9.2 or 8.7 deck Ht for Ford 351 modified circle track. (must be 3.5 stroke)

[rodb63]

Need advice on this, Getting back into boat racing. Starting with a better engine program.
Building a Ford 351 (368 ci max), N-heads, must be stock stroke 3.5, will have about 630 HP when I'm done. will race between 6400 and 8000 RPM.
QUESTION, I'm seeing benefits of the 8.7 deck height, there are some VERY smart people here so I'm after your advice.

Should I go 8.7 or 9.2 deck height. (More rules below) THANK YOU!

(Rules also say Unported Iron heads, 600 HP Holley 4bbl. only, Any compression, roller cam ok, any over the counter intake, *Stoke stroke, valves max int 2.125, ex 1.71, any ignition, dry sump, fuel pump, open headers).
I plan to use a Super victor intake this time.
Thanks a bunch.
RB

[Brian Gray]

I'll go with the taller deck and longer rod. jmo

[Necrosis]

Short deck, 1" c/h piston.

[Nobody]

Research your combo/stroke/rod your thinking about and check out the amount of piston shirt exposed at the bottom of the cylinder that is typical with that combo and deck hieght. Not a real familiar with all the combo's on the fords but on many of the 302 block based engines have issues with piston skirts getting hung way out the bottom of the cylinders at BDC.

[dereksehi]

If you are going to go with a 3.5 inch stroke I would stick with the 9.2 block with a longer connecting rod as mentioned the 302 based strokers especially the 347 had problems scuffing the pistons due to to much of the piston leaving the bottom of the bore and allowing the piston to rock in the bore and scuff the skirts.

[rodb63]

Thanks guys!!
I had 2 engines before, both the same with a 9.2 deck, 6.2 rods. Worked well although I did see some scuffing on the skirts, not a lot. (I won many races too) Then the rules changed adding a roller cam, and allowing the pro topline iron heads, (any iron heads).
Now wanting to get back in with the best possible Ford Iron head engine, recently I did some research, and with an 8.7 deck I could get away with using a 5.95 Ford length rod, which according to some was still a good rod To stroke ratio, but of course the rod to stroke with the 6.2 rod was better.
I was guessing with the changes in recent years as to rod to stroke ratio being of less worries, I would get a lot of guys telling me to do the 8.7 deck. So far thats not true. The 9.2 deck with 6.2 rods did work well. I thought the 8.7 would reduce weight of the engine (30 or 35 lbs) plus the rotating assy. I have no idea about the skirt coming out too far of the bore, thanks for that thought.
Those older engines I had 11-1 cr, victor jr intake, and flat tappet cam .555 gross lift. This time per rules I will have 14.5 at least cr, a super victor intake, and a larger roller cam. This time??
Thats why I asked here.

THANKSs a million!!
RB

[rodb63]

I'm not ruling out the 8.7 !!! I hope to get more responses. and IM some.
Thanks in advance!

[Nobody]

As long as you don't have an issue with the pistons way out the bottom of the bore, myself I'd go with the shorter deck and get rid of the weight. I'm just not familiar enough to tell you what combo's all have that issue, I know several of the 302 blocks have difference amounts of total length on the cylinders which has an effect on the piston out the bottom of the bore. So block brand and/or year choice will likely have a big effect on what is combo's are acceptable and what is iffy.

[rodb63]

Thanks, with that you should know I plan to get ALL 100% new parts, either the latest Ford Racing block, or a Dart all race block. I'm leaning towards the Dart. This will also be a dry sump, probably 4 stage like before.
This time all Ti valves, 2.05, 1.6 which is about the best you can do on the N-heads.
I expect this engine to cost around $20,000, maybe more.
(Before I had a Ford Nascar block and an R block) (not todays nascar blocks as they are all different.)

[Hurst390]

If 3.5 is the max stroke I would vote for the short deck...less weight as said previously..

[Necrosis]

And don't worry about rod/stroke ratio, it is almost entirely meaningless. The way to choose it--design the best piston for your application, know your deck height and stroke, and pick a rod to connect the two. A great piston will pay 1,000x more dividends than worrying about rod ratio.

[TBRE]

Use the 9.2 block, cut down to 9.00.....TB

[mod71m]

With those heavy N heads you better go with the 8.7" deck block if you want to compete against the Chevy motors in the weight department. Engine wight is much more critical than an extra couple horsepower in most circle track cars. Especially dirt cars with the power range you are dealing with.

With an aftermarket 8.7" block and N heads you will still be the same weight if not heavier than an aftermarket Chevy block (SHP block) with Dart heads (or whatever head you prefer).

[fastford]

you are right mod , engine weight is way more critical , we use 302 mex blocks, put a stud girdle on it and fill water jackets with moroso hard block up to the freeze out plugs, this is the best all steel combo we ever ran , I don't like the odd ball 8.7 stuff, in my opinion, the early 9.2 r block is better, but getting as hard to find as the mex block, one thing to remember with the n head and the 302 block, to much timing and it will bust through the cam tunnels, stay at 28 to 30 total and you will be fine, one more thing, be sure to use coated skirt pistons, the short rod angle is rough on pistons and this coating greatly helps, sorry about the rant, I just don't get to talk about my little ford engines on here to much...lol

[let-r-eat]

I'm not a ford guy but if it's a 362 cubic inch rule I wouldn't get too caught up on that 3.5 stroke. I'd be looking at opening the bore up so the engine could breath and use whatever stroke fit the rules.